Kinetic energy and gravitational potential energy are two of the most commonly tested energy types in IGCSE Physics, appearing in questions about falling objects, roller coasters, and energy transformations.
1. What is Kinetic Energy?
Kinetic energy is the energy an object possesses due to its motion, calculated using KE = ½mv², where m is mass in kilograms and v is speed in metres per second. Because speed is squared, doubling an object's speed quadruples its kinetic energy.
2. What is Gravitational Potential Energy?
Gravitational potential energy is the energy an object has due to its height above a reference point, calculated using GPE = mgh, where m is mass, g is gravitational field strength, and h is height in metres.
3. Energy Transformation Between KE and GPE
As an object falls, its gravitational potential energy converts into kinetic energy, and assuming no energy is lost to air resistance, the total mechanical energy remains constant. This principle is frequently used in IGCSE questions involving falling objects or pendulums.
4. Worked Example Approach
For a ball dropped from a height, students can calculate its GPE at the top, set it equal to its KE just before impact, and solve for its final speed — a classic application of the conservation of energy in numerical questions.
Frequently Asked Questions
What happens to kinetic energy when speed doubles?
Kinetic energy increases four times when speed doubles, because kinetic energy is proportional to the square of speed.
Does gravitational potential energy depend on mass?
Yes, gravitational potential energy is directly proportional to an object's mass, along with its height and gravitational field strength.
Conclusion
Understanding how kinetic and gravitational potential energy convert into each other is essential for mastering energy conservation questions in the IGCSE Physics exam.